1. Field of the Invention
The present invention relates to a humidifier employing hollow fiber membranes and adapted for use in a fuel cell system.
2. Description of Related Art
An example of a conventional humidifier is disclosed in Japanese Patent Application Laid-open Publication No. 2002-66262. The disclosed humidifier arranges a bundle of hollow fiber membranes having a vapor permeation property in a cylindrical tube to form a hollow-fiber-membrane module. The cylinder is provided at a first end of a circumferential wall with a humidified gas outlet and at a second end of a circumferential wall with an inlet of dry gas (gas to be humidified).
The module is provided at its axial ends with first and second header blocks, respectively, which are fastened together with through-bolts.
The first header block has a wet gas introducing passage and a humidified gas discharging passage. The wet gas introducing passage is connected to the first end of tube, and communicating with each hollow fiber membrane. The humidified gas discharging passage is connected to the humidified gas outlet The second header block has a wet gas discharging passage and a dry gas introducing passage. The humidified gas discharging passage is connected to the second end of tube, and communicating with each hollow fiber membrane. The dry gas introducing passage is connected to the dry gas inlet.
To the first end of tube is supplied a wet gas, which is passed through the inside of the hollow fiber membranes, and is discharged from the second end of tube. To the dry gas inlet is supplied a dry gas to be humidified, which is passed along the outside of the hollow fiber membranes in the tube, and is discharged from the humidified gas outlet. Therealong, moisture is transmitted between the inside and outside of the hollow fiber membranes to humidify the dry gas to be humidified.